linux-kernel - [PATCH 2/2] sched: Use fair:prio_changed() instead of ad-hoc implementation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20191203160106.18806-3-frederic@kernel.org>
Date:   Tue,  3 Dec 2019 17:01:06 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: [PATCH 2/2] sched: Use fair:prio_changed() instead of ad-hoc implementation

set_user_nice() implements its own version of fair::prio_changed() and
therefore misses a specific optimization towards nohz_full CPUs that
avoid sending an resched IPI to a reniced task running alone. Use the
proper callback instead.

Reported-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
---
 kernel/sched/core.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 90e4b00ace89..66d1af94455e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4540,17 +4540,17 @@ void set_user_nice(struct task_struct *p, long nice)
 	p->prio = effective_prio(p);
 	delta = p->prio - old_prio;
 
-	if (queued) {
+	if (queued)
 		enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
-		/*
-		 * If the task increased its priority or is running and
-		 * lowered its priority, then reschedule its CPU:
-		 */
-		if (delta < 0 || (delta > 0 && task_running(rq, p)))
-			resched_curr(rq);
-	}
+
 	if (running)
 		set_next_task(rq, p);
+	/*
+	 * If the task increased its priority or is running and
+	 * lowered its priority, then reschedule its CPU:
+	 */
+	p->sched_class->prio_changed(rq, p, old_prio);
+
 out_unlock:
 	task_rq_unlock(rq, p, &rf);
 }
-- 
2.23.0